Light-scattering spectroscopy entails illuminating a substance and analyzing light rays scattered from the substance. Conventionally, a fiber optic probe assembly is provided to illuminate the substance and to guide collected light rays into a spectrometer. The fiber optic probe assembly includes an optical fiber with a first or proximal end connected proximate to a laser source and a second or distal end that terminates at a probe tip. The optical fiber guides light rays emitted from a laser source to the probe that illuminates the substance being examined. The fiber optic probe assembly includes a different set of optical fibers having first or distal ends located at the probe and second or proximal ends coupled proximate to the spectrometer. The probe collects light rays scattered by the substance. The different set of optical fibers guides the light rays collected at the probe tip to a spectrometer for analysis.
Raman spectroscopy and other spectroscopies employing optical fibers have limitations that make the technology challenging for medical and other applications. For example, in Raman spectroscopy there is a balance between gathering sufficient light rays through the optical fibers to provide fast acquisition times and having sufficient spectral resolution to identify compounds in a sample or substance. Furthermore, the Raman effect provides very weak signals such that Raman emissions collected at the probe may be one millionth or even less as intense as the exciting radiation that illuminates the sample or sub stance.
Additionally, there are challenges introduced by the spectroscopy equipment itself. Typically, the fiber optic probe assembly includes a connector having a linear bundle of optical fibers that must be aligned with an entrance slit at the spectrometer. A technician aligns the linear bundle by rotating a round connector while monitoring light levels in the spectrometer. Once optimized, the technician tightens down a threaded portion of the round connector to lock the linear bundle in place. During medical procedures, the fiber optic probe assembly may be unplugged from the spectrometer for sterilization or resterilization and replaced after each procedure. The linear bundle in the connector must be aligned with the entrance slit at the spectrometer in a same way each time to allow repeatability of results. A small rotational misalignment of the linear bundle may introduce significant positional misalignment and positional variations on every reconnection. This may result in a reduced signal strength and low performance for the chemometric model. Other drawbacks exist.